Electron emission device and electron emission display using the same

ABSTRACT

An electron emission device includes a substrate, first electrodes formed on the substrate, electron emission regions electrically connected to the first electrodes, and second electrodes placed over the first electrodes such that the second electrodes are insulated from the first electrodes. The second electrodes have openings to expose the electron emission regions. A third electrode is placed over the second electrodes such that the third electrode is insulated from the second electrodes. The third electrode has openings communicating with the openings of the second electrodes. Each of the electron emission regions and the second electrodes simultaneously satisfy the following conditions:
 
 D 2 /D 1≦0.579  (1),
 
and
 
D2≧1 μ  (2)
 
     where D 1  indicates the width of each of the openings of the second electrode, and D 2  indicates the width of each of the electron emission regions.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Application No. 2006-16404filed on Feb. 20, 2006 in the Korean Intellectual Property Office, thedisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Aspects of the present invention relate to an electron emission device,and in particular, to an electron emission device having a predeterminedratio of a width of an electron emission region to a width of an openingof a gate electrode, and an electron emission display using the electronemission device.

2. Description of the Related Art

Generally, electron emission elements are classified into differenttypes depending on the types of electron sources. These include a firsttype using a hot cathode and a second type using a cold cathode.

The second type electron emission elements using a cold cathode includea field emission array (FEA) type, a surface-conduction emission (SCE)type, a metal-insulator-metal (MIM) type, and ametal-insulator-semiconductor (MIS) type.

The FEA-type electron emission element has an electron emission regionand driving electrodes, such as a cathode electrode and a gateelectrode. The FEA-type electron emission element is based on theprinciple that when an electric field is applied to the electronemission region under a vacuum, electrons are easily emitted from theelectron emission region. The electron emission region is formed with amaterial having a low work function or a high aspect ratio, such as acarbonaceous material or a nanometer-sized material.

Several of the electron emission elements are arranged on a firstsubstrate into arrays to make an electron emission device, and theelectron emission device is combined with a second substrate having alight emission unit with a phosphor layer and an anode electrode. Thesecomponents are used to construct an electron emission display.

With the common FEA-type electron emission display, cathode electrodes,an insulating layer, and gate electrodes are sequentially formed on thefirst substrate, and openings are formed at the gate electrodes and theinsulating layer to partially expose the cathode electrodes. Electronemission regions are formed on the cathode electrodes within theopenings. Phosphor layers and the anode electrode are formed on asurface of the second substrate facing the first substrate.

The cathode and the gate electrodes are stripe-patterned and formed tocross each other, and each crossed area of the cathode and gateelectrodes forms a pixel. The electron emission regions are placed at apredetermined domain of the pixel such that the electron emissionregions are spaced apart from each other by a distance.

When predetermined driving voltages are applied to the cathode and thegate electrodes, electric fields are formed around the electron emissionregions at the pixels where the voltage difference between the twoelectrodes exceeds a threshold value, and electrons are emitted fromthose electron emission regions. The emitted electrons are attracted bya high voltage applied to the anode electrode, and directed toward thesecond substrate. When the emitted electrons reach the second substrate,the emitted electrons collide against the phosphor layers at therelevant pixels and cause emission of light.

With the above structure, an insulating layer and a focusing electrodemay be further formed over the gate electrodes to focus the electronbeams. The focusing electrode receives 0V or a negative direct current(DC) voltage of several to several tens of volts, and exerts a repulsiveforce to the emitted electrons passing through the opening in the gateelectrodes and the insulating layer to focus those electrons in thecenter of a stream of electrons.

Meanwhile, unlike the cone-shaped Spindt-type emitters proposed in theearly stages of the electron emitter design, the electron emissionregion may be formed with a layer having an electron emission materialon the surface thereof, mainly through the easily-controlled screenprinting process.

Electron beams from the electron emission display having the layeredelectron emission regions and the focusing electrode include main andsub electron beams within the stream of electron beams. The mainelectron beams are existent among the stream of electron beams togetherwith sub electron beams. The sub electron beams are placed external tothe main electron beams. The width of each of the sub electron beams islarger than that of the main electron beam, and the intensity of each ofthe sub electron beam is weaker than that of the main electron beam.

Accordingly, the phosphor layer is demarcated into a primary lightemission area based on the main electron beam and a secondary lightemission area based on the sub electron beam when light is emitted. Incase the sub electron beam is widely diffused to neighboringdifferent-colored phosphor layers, those different-colored phosphorlayers are excited so that the color purity deteriorates.

The sub electron beam causing the secondary light emission is generateddue to the phenomenon where the electrons emitted from the edge of theelectron emission region are attracted by the gate electrode, and someof the electrons passing close to the focusing electrode are radicallybent to the opposite side by the negative electric field of the focusingelectrode.

In order to prevent the sub electron beams from being generated, it hasbeen conventionally proposed that the shape or size of the opening ofthe focusing electrode should be altered, or the dimension of thefocusing voltage should be controlled. However, when the width of theopening of the focusing electrode is enlarged or the focusing voltage israised to prevent the generation of the sub electron beams, the width ofthe main electron beam is instead enlarged to thereby increase the widthof the primary light emission area, even though the sub electron beamsare prevented from being generated, and thereby decreasing the secondarylight emission.

SUMMARY OF THE INVENTION

Accordingly, various aspects of the present invention includes anelectron emission device which reduces the sub electron beams from beinggenerated to minimize the secondary light emission while not largelyinfluencing the main electron beams, and an electron emission displayusing the electron emission device.

In an aspect of the present invention, the electron emission deviceincludes a substrate, first electrodes formed on the substrate, electronemission regions electrically connected to the first electrodes, andsecond electrodes placed over the first electrodes such that the secondelectrodes are insulated from the first electrodes. The secondelectrodes have openings to expose the electron emission regions. Athird electrode is placed over the second electrodes such that the thirdelectrode is insulated from the second electrodes. The third electrodehas openings communicating with the openings of the second electrodes.Each of the electron emission regions and the second electrodessimultaneously satisfy the following conditions:D2/D1≦0.579  (1),andD2≧1 μm  (2)where D1 indicates the width of each of the openings of the secondelectrode, and D2 indicates the width of each of the electron emissionregions.

The electron emission regions and the openings of the second electrodesmay be serially arranged in the direction of the length of the firstelectrodes, and D1 and D2 are measured in the direction of the width ofthe first electrodes.

The electron emission regions and the openings of the second electrodesmay be formed in the shape of a circle.

Each of the electron emission regions may be formed as any one of anelectron emission layer formed entirely of an electron emission materialand an electron emission layer having an electron emission materialformed on a surface thereof.

The third electrode may have one of the openings at each crossed area ofthe first and the second electrodes.

It is possible that any one of the first and the second electrodes is ascan electrode, and the other of the first and second electrodes is adata electrode, while the third electrode is a focusing electrode.

In another exemplary embodiment of the present invention, the electronemission display includes first and second substrates facing each otherwith a predetermined distance, first electrodes formed on the firstsubstrate, electron emission regions electrically connected to the firstelectrodes, and second electrodes placed over the first electrodes suchthat the second electrodes are insulated from the first electrodes. Thesecond electrodes have openings to expose the electron emission regions.A third electrode is placed over the second electrodes such that thethird electrode is insulated from the second electrodes. The thirdelectrode has openings communicating with the openings of the secondelectrodes. Phosphor layers are formed on a surface of the secondsubstrate. A fourth electrode is placed on a surface of the phosphorlayers. The electron emission regions and the second electrodessimultaneously satisfy the following conditions:D2/D1≦0.579  (1),andD2≧1 μm  (2)where D1 indicates the width of each of the openings of the secondelectrode, and D2 indicates the width of each of the electron emissionregions.

The phosphor layers may include red, green, and blue phosphor layersalternately arranged in a first direction on the second substrate, andD1 and D2 may be measured perpendicular to the first direction on thesecond substrate.

The electron emission regions and the openings of the second electrodesmay be serially arranged in a second direction perpendicular to thefirst direction on the second substrate.

An aspect of the present invention includes an electron emissionstructure, including: a first electrode; an electron emission region toemit an electron stream and formed on the first electrode; and a secondelectrode and formed perpendicularly to the first electrode, wherein thesecond electrode further comprises a hole sized and positioned tocorrespond to the electrode emission region so that a main electron beamand a sub electron beam of the electron stream emitted from the electronemission region have substantially equal width at a predetermineddistance from the electron emission region.

Additional aspects and/or advantages of the invention will be set forthin part in the description which follows and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will becomeapparent and more readily appreciated from the following description ofthe aspects, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 is a partial exploded perspective view of an electron emissiondisplay according to an aspect of the present invention.

FIG. 2 is a partial sectional view of an electron emission display shownin FIG. 1.

FIG. 3 is a partial amplified plan view of the electron emission deviceaccording to an aspect of the present invention.

FIG. 4 is a partial amplified plan view of an electron emission deviceillustrating a variant of a focusing electrode.

FIG. 5 schematically illustrates the trajectories of the electron beamsemitted from the center of an electron emission region of an electronemission display according to an aspect of the present invention.

FIG. 6 schematically illustrates the trajectories of the electron beamsemitted from the edge of an electron emission region of an electronemission display according to an aspect of the present invention.

FIG. 7 is a graph illustrating the widths of main and sub electron beamsmeasured when the ratio of a width of an electron emission region to awidth of an opening of a gate electrode of an electron emission displayis varied according to an aspect of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the aspects of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The aspects are described below in order to explain thepresent invention by referring to the figures.

As shown in FIGS. 1 to 3, an electron emission display includes firstand second substrates 10 and 12 facing each other with a predetermineddistance. A sealing member (not shown) is provided at the peripheries ofthe first and the second substrates 10 and 12 to seal them to eachother, and the inner space between the substrates 10 and 12 is evacuatedto about 10⁻⁶ Torr. In this way, the first and the second substrates 10and 12 and the sealant forms a vacuum vessel.

Arrays of electron emission elements are arranged on a surface of thefirst substrate 10 facing the second substrate 12. The arrays ofelectron emission elements are used to construct an electron emissiondevice 100 on the first substrate 10. The electron emission device 100is assembled with the second substrate 12 and a light emission unit 110provided on the second substrate 12 to construct an electron emissiondisplay.

As parts of the electron emission device 100, cathode electrode orelectrodes 14 (first electrodes) are stripe-patterned (or bands) formedon the first substrate 10 and extend in a direction of the firstsubstrate 10. A first insulating layer 16 is formed on the entiresurface of the first substrate 10 such that first insulating layer 16covers the cathode electrodes 14. Gate electrode or electrodes 18(second electrodes) are stripe-patterned (or bands) formed on the firstinsulating layer 16 and extend in a direction substantiallyperpendicular to the cathode electrodes 14.

When the crossed (or intersected) areas of the cathode and the gateelectrodes 14 and 18 are defined as pixels, electron emission region orregions 20 are formed on the cathode electrodes 14 of the respectivepixels. To expose the electron emission regions 20 on the firstsubstrate 10, openings 161 and 181 are formed respectively at the firstinsulating layer 16 and the gate electrodes 18 corresponding to therespective electron emission regions 20.

The electron emission region 20 is formed with a material (electronemission material) that emits electrons when an electric field isapplied thereto under a vacuum. Such a material includes a carbonaceousmaterial or a nanometer (nm) size material. For instance, the electronemission region 20 may be formed with carbon nanotube, graphite,graphite nanofiber, diamond, diamond-like carbon, fullerene C₆₀, siliconnanowire, or a combination thereof.

The electron emission regions 20 are formed with an electron emissionlayer (not shown) having a predetermined thickness and a predeterminedwidth. The electron emission layer may be formed entirely of an electronemission material, or of a structure having the electron emissionmaterial formed on the surface thereof. The electron emission region 20may be formed through screen printing, direct growth, chemical vapordeposition, and/or sputtering.

In various aspects, the electron emission regions 20 are seriallyarranged on the respective pixels in the direction of the length of anyone of the cathode and the gate electrodes 14 and 18. For example, asshown in FIG. 1, the electron emission regions 20 are arranged in thelongitudinal direction of the cathode electrode 14. Each of the electronemission regions 20 and the openings 181 of the gate electrode 18 may beformed in the shape of a circle. In other aspects, the shape of theelectron emission regions 20 and the openings 181 of the gate electrode18 may be an oval, a rectangle, or others. Also, within a grouping ofthe electron emission regions 20 and the openings 181, an individualelectron emission region 20 or an opening 181 may be shaped differentlyfrom the others.

A focusing electrode 22 (a third electrode) is formed on the gateelectrodes 18 and the first insulating layer 16. A second insulatinglayer 24 is placed under the focusing electrode 22 to insulate the gateand the focusing electrodes 18 and 22 from each other. To pass theelectron beams, openings 221 and 241 are also respectively formed in thefocusing electrode 22 and the second insulating layer 24. In variousaspects of the present invention, the first, second, and thirdelectrodes 14, 18, 22 form a step structure as shown in FIG. 2.

As shown in FIGS. 1 and 3, one opening 221 may be formed in the focusingelectrode 22 at each pixel to collectively focus the electrons emittedfrom each pixel. Alternatively, as shown in FIG. 4, one opening 222 isformed at the focusing electrode 22′ per each electron emission region20 to separately focus the electrons from the respective electronemission regions 20.

As parts of the electron emission display, in various aspects of thepresent invention, phosphor layers 26 are formed on a surface of thesecond substrate 12 facing the first substrate 10. The phosphor layers26 have red, green, and blue phosphor layers 26R, 26G, and 26B such thatthey are spaced apart from each other by a distance. A black layer 28 isdisposed between the respective red, green, and blue phosphor layers26R, 26G, and 26B to enhance the screen contrast. Each of the coloredphosphor layers 26R, 26G, and 26B is placed in each pixel, and the red,green and blue phosphor layers 26R, 26G, and 27B are alternatelyarranged in the corresponding longitudinal direction of the gateelectrode 18.

An anode electrode 30 is formed on the phosphor and the black layers 26and 28. The anode electrode 30 may be a metallic material, such asaluminum Al. The anode electrode 30 receives a high voltage required toaccelerate electron beams from the electron emission regions 20, makesthe phosphor layers 26 be in a high potential state, and reflectsvisible rays radiated from the phosphor layers 26 toward the secondsubstrate 12 to heighten the screen luminance.

In various aspects, the anode electrode 30 may be formed with atransparent conductive material, such as indium tin oxide (ITO). In sucha case, the anode electrode 30 is placed on a surface of the phosphorand the black layers 26 and 28 that face toward the second substrate 12.It is also possible that a transparent conductive layer (such as ITO)and a metallic layer (such as Al) are both formed to function as theanode electrode 30.

As shown in FIG. 2, spacers 32 are disposed between the first and thesecond substrates 10 and 12 to support the pressure applied to thevacuum vessel and constantly sustain the distance between the twosubstrates 10 and 12. The spacers 32 are located at correspondinglocations to the black layers 28 such that the spacers 32 do not intrudeupon the phosphor layers 26.

The above-structured electron emission display is driven by supplyingpredetermined voltages to the cathode electrodes 14, the gate electrodes18, the focusing electrode 22, and the anode electrode 30.

During operation of the electron emission display, one of the cathodeand the gate electrodes 14 and 18 receives a scan driving voltage tofunction as a scan electrode, and the other electrode receives a datadriving voltage to function as a data electrode. The focusing electrode22 receives a voltage required for focusing the electron beams, such as0V or a negative direct current (DC) voltage of several to several tensof volts. The anode electrode 30 receives a voltage required foraccelerating the electron beams, such as a positive direct current (DC)voltage of several hundreds to several thousands of volts.

During operation of the electron emission display, an electric field isformed around the electron emission regions 20 at the pixels where thevoltage difference between the cathode and the gate electrodes 14 and 18exceeds a threshold value, and electrons are emitted from those electronemission regions 20. The emitted electrons pass through the openings 221of the focusing electrode 22, and are focused at the center of thestream of electron beams. The emitted electrons are attracted by thehigh voltage applied to the anode electrode 30, collide against thephosphor layers 26 at the relevant pixels, and cause emission of light.

FIGS. 5 and 6 show the trajectories of the electron beams emitted fromor near the center of the electron emission region 20 and from or nearthe edge thereof, respectively. Shown is the sectional view of theelectron emission device 100 taken in the direction of the width of thecathode electrode 14 (in the x axis direction of the drawing FIGS. 1-6)and the trajectories of the electron beams.

As shown in FIG. 5, the left and the right sides of the stream ofelectron beams emitted from or near the center of the electron emissionregion 20 are symmetrical or substantially symmetrical to each otherwith respect to a center of the stream. The electron beams are diffused(or fanned out) toward the second substrate (not shown), and areentirely of main electron beams without sub electron beams.

Meanwhile, as shown in FIG. 6, the electrons emitted from or near theedge of the electron emission region 20 are biased to the gate electrode18 in the side direction, and proceed toward the second substrate (notshown) to join the main electron beams. However, some of the electronspassing close to the focusing electrode 22 are radically bent away fromthe main electron beams by the negative (or the opposite) electric fieldof the focusing electrode 22 to thereby form the sub electron beams.

In this way, the sub electron beams with a width larger than the mainelectron beams are formed external to (or outside of) the main electronbeams due to the electrons that are mainly emitted from or near the edgeof the electron emission region 20. Accordingly, a secondary lightemission area based on the sub electron beams is formed on the phosphorlayer 26 external to (or outside of) the primary light emission area ofthe phosphor layer 26 or the pixel.

The secondary light emission occurs because the electron emission region20 has a relatively wide electron emission area as it is formed with anelectron emission layer having a predetermined width, which is differentfrom the Spindt type electron emitter of the conventional art.

To reduce the secondary light emission, the electron emission displayaccording to an aspect of the present invention has a predeterminedratio of a width of the electron emission region 20 to a width of theopening 181 of the gate electrode 18 to thereby reduce and/or preventthe sub electron beams from being generated. In this aspect, theelectron emission region 20 and the gate electrode 18 are structured tosatisfy the following condition:D2/D1≦0.579  (1)

where D1 and D2 indicate the width of the opening 181 of the gateelectrode 18 and the width of the electron emission region 20,respectively. The D1 and D2 are measured in the neighboring direction ofthe different-colored phosphor layers 26R, 26G, and 26B (that is, in thedirection of the width of the cathode electrode 14). In an aspect wherethe electron emission region 20 and the opening 181 of the gateelectrode 18 are formed in the shape of a circle, D1 and D2 may indicatethe diameter of the opening 181 of the gate electrode 18 and thediameter of the electron emission region 20, respectively.

FIG. 7 is a graph illustrating the widths of the main and the subelectron beams that collide with the phosphor layer 26 measured whilethe ratio of the width of the electron emission region 20 to the widthof the opening 181 of the gate electrode 18 is varied. The widths of themain and the sub electron beams illustrated in the graph indicate thewidths thereof measured in the neighboring direction of thedifferent-colored phosphor layers 26R, 26G, and 26B.

According to an aspect of the electron emission display, the thicknessof the first insulating layer 16 was established to be 3 μm, the widthof the opening 181 of the gate electrode 18 was established to be 15 μm,the thickness of the second insulating layer 24 was established to be 4μm, and the width of the opening 221 of the focusing electrode 22 wasestablished to be 38 μm. Also, the widths of the main and the subelectron beams were measured while varying the width of the electronemission region from 2 μm to 12 μm. Also, as to the driving conditions,the cathode voltage was established to be 20V, the gate voltage wasestablished to be 80V, the focusing voltage was established to be 0V,and the anode voltage was established to be 8 kV.

As shown in FIG. 7, as the width ratio D2/D1 of the electron emissionregion 20 to the opening 181 of the gate electrode 18 is increased, thewidth of the main electron beam is gradually reduced while the width ofthe sub electron beam is radically enlarged. Particularly, when thewidth ratio D2/D1 of the electron emission region 20 to the opening 181of the gate electrode 18 exceeds 0.579, the width of the sub electronbeam increases beyond the width of the main electron beam. When theratio D2/D1 is above 0.579, a secondary light emission area is present.As shown in FIG. 7, the ratio D2/D1 of 0.579 represents a situation whenthe width of the main electron beam and the width of the sub electronbeams are essentially equal. In one aspect of the present invention, thewidths of the main and sub electron beams are about 175 μm.

As discussed above, according to the aspect of the present invention,the ratio of the width D2 of the electron emission region 20 to thewidth D1 of the opening 181 of the gate electrode 18 should be less than0.579, although not required. As a result, the generation of the subelectron beams is effectively reduced without radically reducing thewidth of the main electron beam.

Meanwhile, it is preferable, though not required, that the electronemission region 20 has a width of 1 μm or more. When the electronemission region 20 has a width of less than 1 μm, it is difficult topattern (or fabricate) the electron emission regions 20. In particular,there is a difficulty in the light exposure process during itsfabrication, which occurs after a paste mixture containing an electronemission material and a photosensitive material is printed on the entiresurface of the first substrate, and selectively hardened through thelight exposure. Afterwards, the non-hardened portions are removedthrough the developing process to form the electron emission regions 20.

Furthermore, when the electron emission region has a width of less than1 μm, the amount of discharge current from the electron emission regionis reduced, and hence, the driving voltage needs to be raised.Accordingly, the driving voltage of the electron emission region havinga width of 2 μm should be raised by three times to that of the electronemission region having a width of 6 μm and the driving voltage of theelectron emission region having a width of 1 μm should be raised by sixtimes to that of the electron emission region having a width of 6 μm.Accordingly, in this aspect, the electron emission region 20 is formedwith a width of at least about 1 μm.

As described above, with the electron emission display according to theaspects, as the electron emission region 20 and the gate electrode 18are structured to satisfy the above-identified conditions, the secondarylight emission is reduced to thereby enhance the color purity, and anoptimum light emission area is obtained so that the emission efficiencyof the electron emission region 20 is heightened even with a lowerdriving voltage.

Although a few aspects of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in the aspects without departing from the principlesand spirit of the invention, the scope of which is defined in the claimsand their equivalents.

1. An electron emission device comprising: a substrate; first electrodesformed on the substrate; electron emission regions electricallyconnected to the first electrodes; second electrodes placed over thefirst electrodes such that the second electrodes are insulated from thefirst electrodes, the second electrodes having openings to expose theelectron emission regions; and a third electrode placed over the secondelectrodes such that the third electrode is insulated from the secondelectrodes, the third electrode having openings communicating with theopenings of the second electrodes; wherein each of the electron emissionregions and the second electrodes simultaneously satisfy the followingconditions:D2/D1≦0.467  (1)andD2≧1 μm  (2) where D1 indicates the width of each of the openings of thesecond electrodes, and D2 indicates the width of each of the electronemission regions.
 2. The electron emission device of claim 1, wherein D1and D2 are measured in the direction of the width of any one of thefirst and the second electrodes.
 3. The electron emission device ofclaim 2, wherein the electron emission regions and the openings of thesecond electrodes are serially arranged in the direction of the lengthof the first electrodes, and D1 and D2 are measured in the direction ofthe width of the first electrodes.
 4. The electron emission device ofclaim 2, wherein the electron emission regions and the openings of thesecond electrodes are formed in the shape of a circle.
 5. The electronemission device of claim 1, wherein each of the electron emissionregions is formed as any one of an electron emission layer formedentirely of an electron emission material and an electron emission layerhaving an electron emission material formed on a surface thereof.
 6. Theelectron emission device of claim 5, wherein the electron emissionregion comprises at least one of carbon nanotube, graphite, graphitenanofiber, diamond, diamond-like carbon, fullerene C₆₀, and siliconnanowire.
 7. The electron emission device of claim 3, wherein the thirdelectrode has one of the openings at each crossed area of the first andthe second electrodes.
 8. The electron emission device of claim 1,wherein any one of the first and the second electrodes is a scanelectrode, and the other of the first and the second electrodes is adata electrode, while the third electrode is a focusing electrode.
 9. Anelectron emission display comprising: first and second substrates facingeach other with a predetermined distance; first electrodes formed on thefirst substrate; electron emission regions electrically connected to thefirst electrodes; second electrodes placed over the first electrodessuch that the second electrodes are insulated from the first electrodes,the second electrodes having openings to expose the electron emissionregions; a third electrode placed over the second electrodes such thatthe third electrode is insulated from the second electrodes, the thirdelectrode having openings communicating with the openings of the secondelectrodes; phosphor layers formed on a surface of the second substrate;and a fourth electrode placed on a surface of the phosphor layers;wherein the electron emission regions and the second electrodessimultaneously satisfy the following conditions:D2/D1≦0.467  (1)andD2≧1 μm  (2) where D1 indicates the width of each of the openings of thesecond electrodes, and D2 indicates the width of each of the electronemission regions.
 10. The electron emission display of claim 9, whereinthe electron emission regions and the openings of the second electrodesare serially arranged in the direction of the length of the firstelectrodes, and D1 and D2 are measured in the direction of the width ofthe first electrodes.
 11. The electron emission display of claim 9,wherein the electron emission regions and the openings of the secondelectrodes are formed in the shape of a circle.
 12. The electronemission display of claim 9, wherein the phosphor layers comprise red,green and blue phosphor layers alternately arranged in a first directionon the second substrate, and D1 and D2 are measured perpendicular to thefirst direction on the second substrate.
 13. The electron emissiondisplay of claim 12, wherein the electron emission regions and theopenings of the second electrodes are serially arranged in a seconddirection perpendicular to the first direction on the second substrate.14. The electron emission display of claim 9, wherein the electronemission region is formed as any one of an electron emission layerformed entirely of an electron emission material and an electronemission layer having an electron emission material formed on thesurface thereof.
 15. The electron emission display of claim 13, whereinthe third electrode has one of the openings at each crossed area of thefirst and the second electrodes.
 16. The electron emission display ofclaim 9, wherein any one of the first and the second electrodes is ascan electrode, and the other of the first and second electrodes is adata electrode, while the third electrode is a focusing electrode, andthe fourth electrode is an anode electrode.
 17. The electron emissiondevice of claim 1, wherein the first, second, and third electrodes forma step structure.
 18. The electron emission display of claim 9, whereinthe first, second, and third electrodes form a step structure.
 19. Anelectron emission structure, comprising: a first electrode; an electronemission region to emit an electron stream and formed on the firstelectrode; and a second electrode formed perpendicularly to the firstelectrode, wherein the second electrode further comprises a hole sizedand positioned to correspond to the electrode emission region so that amain electron beam and a sub electron beam of the electron streamemitted from the electron emission region have substantially equal widthat a predetermined distance from the electron emission region, wherein awidth of the hole of the second electrode and a width of the electronemission region satisfies the following conditions:D2/D1≦0.467  (1)andD2≧1 μm  (2) where D1 is the width of the hole and D2 is the width ofelectron emission region.